Known procedures for measuring corrosion have utilized measurements of the electrical conductivity and/or resistance of samples or probes inserted within the corrosive medium. For example, U.S. Pat. No. 3,104,355 describes use of a pair of relatively thick and thin corrodible metals connected as the legs of a balanced bridge circuit. Since corrosion changes the resistance of the thin element more than that of the thick element, the rate of corrosion is proportionate to changes in the ratio of their resistances. U.S. Pat. No. 3,108,242 describes probes which have relatively large surface areas. Such probes can be coated with a protective material such as paint and used in similar resistance measurements to determine the protective capability of the coating. That patent mentions numerous problems that may be encountered due to a change in the size and shape of such probes. U.S. Pat. No. 3,124,771 describes probes assemblies which can be supported within a fluid-conveying tube and used in similar measurements. Those probes are formed by mounting very thin shim stock on an electrical insulating material in order to obtain a probe which is mechanically strong but has a high sensitivity to corrosion.